It is required to apply a technology for forming a fine pattern to a fabrication process of various optoelectronic devices such as a semiconductor device, an organic light emitting diode (OLED) device, and a light emitting diode (LED) device. This is because desired fine patterns need to be formed according to various necessities such as driving circuit formation, pixel formation, and electrode formation of a device.
In addition, in the case of a biosensor that uses or does not use electricity except for the optoelectronic device, a fine pattern needs to be formed.
In general, as such a technology for forming a fine pattern, various methods such as photolithography, a shadow mask, and printing have been used according to a pattern shape, a pattern condition, and so on. However, the methods have their advantages and disadvantages, one method is not commonly applied to form all types of fine patterns and, an optimal method is generally selected inconsideration of cost utility analysis according to an applied example.
Photolithography is used to form a circuit via a method of applying a thin photoresist with photosensitivity onto a substrate, placing a desired mask pattern over the substrate and, then, applying light to the resultant structure, which is similar to photography, and goes through the following processes.
FIG. 1 is a schematic diagram illustrating a patterning method via general photolithography. As illustrated in FIG. 1, a pattern target material is coated on a surface of a substrate and, then, a photosensitive material is coated on the substrate. Then, a desired mask pattern is put on the resultant structure, an exposure process of irradiating with ultraviolet (UV) light is performed and, then, the photosensitive material is selectively removed using a developing solution. Then, the pattern target material is selectively etched and, then, the photosensitive material on the pattern target material is removed to form a desired pattern. However, photolithography has various problems in that the aforementioned complicated processes are required and the problems will be described below in detail.
The shadow mask is a thin metallic plate with numerous small holes and is used in vapor deposition. A fine metal mask (FMM) of the shadow mask is used for deposition of an organic material with a fine pattern on a large substrate. Accordingly, when the FMM is used, a plurality of desired fine patterns of an organic material may be formed at desired locations of a substrate in one go. For deposition of an organic material with a desired pattern, the FMM may include a plurality of rectangular slots or stripe-type slits through which an organic material passes. Here, the plurality of rectangular slots or stripe-type slits may constitute a unit masking portion and the FMM may include a plurality of unit masking portions. A deposition technology using the FMM may be used to deposit an organic material and to form a cathode in order to manufacture a large-area OLED display device or the like.
In order to manufacture a large-area OLED display device, a large-area substrate is required. However, in the case of a large-area substrate, the substrate may be bent. Accordingly, since an interval between the substrate and a mask is not uniform, there is a problem in that an accurate pattern is not formed at a desired location, resulting in forming defective devices.
Accordingly, there is a limit in manufacture of a large-area OLED display device using a deposition technology using an FMM. That is, when an organic emission layer or a cathode layer is formed on a substrate using the FMM, there is a limit in extending the layer to a large area substrate.
As an organic emission layer needs to be formed in the thin film form, the FMM also needs to be thin. However, when the FMM is thin, manufacture and design in consideration of the case in which the FMM is bent due to external force or self load are difficult and, also, there is a limit in forming the FMM to a thickness equal to or less than 10 μm. That is, when a conventional method using a mask such as an FMM is used, there is a limit in forming an organic emission layer as a thin film.
When a metal mask such as an FMM is used, an organic material is deposited through an open pixel and, in this regard, when the metal mask is repeatedly used for a predetermined time period, the organic material is deposited on the open pixel, changing a pattern size. Accordingly, there is a problem in that a metal mask needs to be replaced at a predetermined period.
As described above, when an FMM scheme is used, there is a significant limit in forming a desired pixel according to a shadowing effect (dead space is generated) during pixel formation due to reasons such as the thickness of a metal mask and an interval with a substrate.
Recently, with regard to manufacture of an optoelectronic device, industrial applications of a single molecule-based high-purity organic material, inorganic material, or hybrid material have drawn attention. In particular, industrial applications of an organic semiconductor based on a deposition-based single molecule or printable polymer have drawn attention due to light, inexpensive, and mechanically flexible characteristics and, as device integration is required, fine patterning of a material of a pattern target layer (active layer) of an organic material has been considered as a very important technology.
As described above, examples of the patterning technology of an organic material broadly include a method using a shadow mask in vapor deposition and a photolithography using a photoresist.
In the case of patterning an organic material using a shadow mask in vapor deposition, it is disadvantageously difficult to pattern the organic material with a high resolution and a high yield for the aforementioned reasons during manufacture of a large-area electronic device array. In addition, when an organic material is patterned using the photolithography method of FIG. 1, it is difficult to pattern an organic material using this method in reality due to dissolution or modification of an organic active layer during coating, developing, and removing processes of a photosensitizer as well as expensive equipment and complicated processes.
Recently, a metal oxide-based material that has optical transparency and high performance and is reported to have excellent stability compared with an organic material has been actively developed. In particular, a metal oxide material for allowing a solution process has drawn attention in that the material is easily applied to a simple process and a large-area. In addition, a metal oxide material has been more actively applied and used in industrial fields related to semiconductor devices and, as integration of devices is required, a material patterning technology has been very importantly considered.
A main method of the patterning technology of the metal oxide material is the aforementioned photolithography method. Although the photolithography method permits high-resolution fine patterning, there are problems in that expensive equipment is required and complicated processes such as coating, exposure, developing, and etching of a photosensitizer are accompanied and, in particular, the material may be dissolved and modified due to material and solvents in processes. In particular, the photolithography method has an actual limit in application to a large-area display market that has been currently and remarkably developed.
Recently, a complicated integration circuit with a multilayer structure or the like has been required to be manufactured. That is, an electronic device has been generally required to be patterned with a high resolution. When a photolithography method is used, it is easy to pattern a general organic and inorganic material. However, it is almost impossible to pattern an organic material using a photolithography method for reasons such as degraded performance of the organic material during deposition and removal of a photoresist due to a solvent used during a patterning process. In the case of patterning an organic material using a shadow mask in vapor deposition, in particular, with regard to manufacture of a large-area electronic device array, it is disadvantageously difficult to achieve multiple-patterning with a high resolution and a high yield for the aforementioned reason.
Korean Patent No. 1463290 discloses a technology that uses the orthogonality of a material and is used to pattern a fluorine (F)-containing material using a photolithography process.
US Patent No. 2010-0289019 discloses a technology that uses a photolithography process and uses CYTOP as a protective layer of an organic semiconductor. U.S. Pat. No. 9,034,737 discloses a technology that uses a photolithography process and uses CYTOP as a protective layer of a photoelectron material.
That is, the above patent documents disclose a technology that uses CYTOP and so on with orthogonality and is used in patterning using a photolithography process. However, as the photolithography process is used, complicated processes such as coating, exposure, developing, and etching of a photosensitizer are required and, also, there is a limit in achieving a large area.
Microelectronic Engineering 123 (2014) 33-37 (Preparation of fluoropolymer structures for orthogonal processing of diverse material by Micro-Contact Printing) discloses a technology that does not uses a photolithography process and is used to transcribe only a desired portion of a polymer film coated on an elastic mold on a substrate via an implant method after a micro contact printing method. The technology does not use a photolithography process and, thus, is capable of simplifying processes but, as the implant method and the micro contact printing method using a mold are used, patterning in a local region is possible but there is a limit in achieving a large area. When the micro contact printing method and/or the implant method are used, a pattern is transcribed on a surface of a substrate while pushing the surface of the substrate at a predetermined pressure and, thus, when the surface of the substrate is pushed at a predetermined pressure or more, there is a problem in that a separate functional layer formed on the surface of the substrate is damaged.
Accordingly, there is a need for a technology of patterning an organic material, an inorganic material, or a hybrid material on a surface of a substrate via a simple process with a high yield and a high resolution. In addition, there is a need for a technology of forming various patterns as a multiple pattern in a right and left direction or forming various patterns as a multilayer pattern in an upper and lower direction as well as for achieving a large area.